Speaker
Haraldur Gunnlaugsson
(Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Århus C, Denmark)
Description
Semiconductors, which are ferromagnetic at room temperature, are strived after as potential multifunctional materials. For ZnO, room temperature ferromagnetism has been achieved by doping with 3d transition metals making potential dilute magnetic semiconductors. However, contradicting results have been obtained and neither the conditions for, nor the origin of the magnetism are as yet understood. Recent theoretical and experimental work have suggested the important role of lattice defects, while other authors have suggested unintentional precipitation, to be the source of the magnetism.
We have performed online 57Fe Mössbauer spectroscopy following implantation of 57Mn (T½ = 1.5 min.). Mössbauer spectroscopy is a powerful tool giving information on the valence state of the Fe, site symmetry and magnetic interactions on an atomic scale.
The Mössbauer spectra obtained after implantation into ZnO show magnetic sextets originating from iron in the ferric state. The formation kinetics of the ferric iron is shown to suggest formation of FeZn-O-VZn defects upon implantation. Measurements in external magnetic field show that these sextets are due to slow paramagnetic relaxations.
Author
Haraldur Gunnlaugsson
(Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Århus C, Denmark)
Co-authors
D. Naidoo
(School of Physics, University of the Witwatersrand, WITS 2050, South Africa)
G. Langouche
(Instituut voor Kern-en Stralingsfysika, University of Leuven, B-3001 Leuven, Belgium)
G. Weyer
(Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Århus C, Denmark)
H. Masenda
(School of Physics, University of the Witwatersrand, WITS 2050, South Africa)
H. P. Gíslason
(Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavík, Iceland)
K. Bharuth-Ram
(School of Pure Physics, University of KwaZulu-Natal, Durban 4041, South Africa)
K. Johnston
(EP Division, CERN, CH-1211 Geneva 23, Switzerland)
M. Fanciulli
(Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, Milano, Italy)
R. Mantovan
(Laboratorio Nazionale MDM CNR-INFM, 20041 Agrate Brianza (MI), Italy)
R. Sielemann
(Hahn-Meitner Institute, D-14109 Berlin, Germany)
S. Ólafsson
(Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavík, Iceland)
T Mølholt
(Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavík, Iceland)
Y. Kobahashi
(The Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-0198, Japan)
Y. Yoshida
(Shizuoka Institute of Science and Technology, Shizuoka 437-8555, Japan)
